Ladder and rung connection



May 4, 1965 c. E. LARSON LADDER AND RUNG CONNECTION 2 Sheets-Sheet 1Filed May 9, 1961 24 CLAYTON E. LARSON r g2. fi w ATTORNEYS y 4, 1965 c.E. LARSON 3,181,651

LADDER AND RUNG CONNECTION Filed May 9, 1961 2 Sheets-Sheet 2 INVENTORCLAYTON E. LARSON ATTORNEYS United Patented May 4, 1965 3,181,651 LADDERAND RUNS QONNEtCTlGN (Jlayton E. Larson, Weston, Conn, assigner to WhiteMetal Rolling & Stamping Corporation, Brooklyn, N.Y., a corporation ofNew York Filed May 9, 1% Ser. No. 193,395 3 Claims. (6i. 182-228) Thisinvention relates to ladders and a method of manufacturing the same.More particularly, it concerns an improved ladder constructionincorporating a novel rung, and a unique method for forming the rungsthereof and connecting them to the ladder siderails.

Because of the functions served by ladders, it is essential that theypossess two basic features, i.e., that they are sufficiently strong tocarry the weight of a person or persons using them, and secondly thatthey be light in weight to facilitate movement from place to place asrequired without the use of special handling equipment. Theserequirements have led to the extended use by ladder designers andmanufacturers or" light metals such as aluminum, magnesium or alloysincluding one or both of these metals, with the result that extremelylight and strong ladders are presently available solely due to theinherent characteristics of these metals. Yet, there remains room forimprovement, particularly in the assembly of the runes between thesiderails and at spaced intervals along the length thereof. In laddersof this type heretofore available, perhaps the most common techniqueemployed in connecting the ladder rungs to the siderail thereof has beento extend a tubular rung through a siderail aperture having a diametersubstantially the same as or slightly larger than the rung diameter andswaging or upsetting the end of the rung outwardly to secure theconnection. Examples of such constructions may be found in US. PatentsNo. 1,912,331 or No. 2,769,70. In other instances, rungs are secured inplace by welding or brazing. Although such connections of the rungs tothe siderails are satisfactory to prevent direct separation of thesecomponents, there results a considerable weakening of the laddersiderail due to the considerably large hole which must be formednecessarily in the siderails or, if welding or brazing is used, due tothe heat stresses imposed on the metal from which the siderails areformed. Also, particularly where swaging or upsetting techniques areemployed, the strength of the connection relies largely on theresistance of the upset portion or" the rung to deformation by bending.When such a ladder is subjected to rough handling, therefore, the severebending stresses which occur between the rung and siderail result in aloosening of the joint and thus, a defective ladder. To circumvent thisproblem, further proposals have been advanced (see, for example, US.Patents No. 2,618,427 and No. 2,552,630), but have resulted in acomparatively complex arrangement which either gives rise to increasedcost of manufacture or adds considerably to the overall weight of theladder or both.

Also, it has been proposed, particularly where wooden siderails are usedwith metallic run s, to form the rungs having projections at their endswhich are passed through the siderails and bent over at their ends toeffect the attachment of the rung to the siderail (see, for example, US.Patents Nos. 1,445,573 and 1,503,880). Such construction afford aminimum of interference with siderail strength, but on the other hand,the only resistance orlercd to separation of the rung from the siderailresides in the bent over portion of the sheet metal prongs and anyfriction which may EXi between the prongs and the siderails in whichthey are imbcdded. As a result, when subjected to rough use, the extr mepull out forces due to bending moments incurred at the connection of therungs to the sidcrails are likely to cause separation of the rung fromthe siderail producing a loose joint, and accordingly an unsafe ladder.

Another problem expericenced in the use of rungs or steps for laddersformed from like metals is the difiiculty in achieving a suitably lightrung section. In rung constructions heretofore available, the directbending moments imposed thereon in use have required suitably heavy rungcross-sections. To some extent, this problem has been mitigated by theuse of tubular rungs but here, the requirement for a sufticient amountof material to etfect the joint between the rung and the siderail hasrestricted the lightness of rung cross-section employed. Althoughobviously, the rung could be built up at its end portions for thispurpose, such would add materially to the cost of manufacture ascompared with a rung having a continuous cross-section throughout itslength.

Accordingly, a principal object of this invention is to provide a newand improved ladder incorporating a novel rung structure and method forits formation as well as a unique method of connecting the rung to theladder siderails by which the aforementioned problems are substantiallyand effectively overcome.

Another object of this invention is the provision of a new and improvedladder construction by which the connection of the rungs to thesiderails may be effected in an extremely economical manner, whichconnection is exceptionally strong and yet in no way sacrifices siderailstrength characteristics or overall ladder weight.

A further object of this invention is that of providing a new andimproved light metal ladder rung or step which is extremely resistant tobending loads imposed thereon while at the same time facilitating anextremely strong and eifective connection of the rung to the laddersiderail in an economical manner without in any way sacrificing overalllightness in weight.

A further object of this invention is the provision of a ladder of thetype referred to in which the rungs are connected to the siderails in amanner such that maximum resistance to angular deformation or bending atthe connection is aiford-ed without removal of any substantial portionof the ladder siderail and resulting weakening thereof.

Another object of this invention is that of providing a ladder rungstructure of the type referred to and method for its manufacture whichis adaptable to all forms of ladder rungs whether they be tubular,channel shaped, round, square or wide tread.

A still further object of this invention is the provision of a new andimproved method for the manufacture of light metal ladders which isextremely economical in practice and which results a ladder havingsuperior strength charact ristics and yet which is extremely light inWeight.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter. It should be understood, however, that the detaileddescription, while indicating preferred embodiments of the invention isgiven by way of illustration only, since it will become apparent tothose skilled in the art from this description that various changes andmodifications can be made without departing from the true spirit andscope of this invention.

In general, the aforementioned objects are accomplished by extruding ali ht metal rung having a crosssection defining a plurality of rod-likerib portions interconnected by relatively thin integral wall portionsand then cutting back the Wall portions at the ends of the rung to leavethe rib portions extending as studs. These studs are then passed throughcorresponding apertures formed in the siderails and riveted or otherwiseexpanded to secure the rung-siderail connection. Preferably, the rungrib portions are arranged to be positioned at the top and bottom of therungs when the ladder is in use to reinforce the rung against thecompressive and tensile stresses which exist at these pointsrespectively. 7 In one form of theinvention, the rung cross-section maybe generally circular. and include at least tworeinforcing rib portionsintegrally formed with a pair of arcuate wall portions, the .wallportions being cut back at the ends to permit the rib portions to extendas studs for riveting to the ladder siderails. Alternatively, the rungcross section may be four sided so as to achieve a flat tread rung andthree or four .rib portions may be formed therein and extended as the(rivet studs. Or, if a wide tread rung of the type used extensively instepladders is to be desired, the rib portions may be formed at thecorners of the step cross section interconnected by at least threeintegral wall portions, which are cut back at their ends to leaveextending the .rib portions in the form of rivet studs. A more completeunderstanding of its various forms may be had by reference to theaccompanying drawings in which: e FIG. 1 is a fragmentary side elevationin partial crosssection of the ladder of this invention; FIG.. 2 .is across section taken along line 2-2 of FIG. 1;

FIG. 3 is a perspective view of an extruded blank from which the ladderrung of this invention is formed;

FIG. 4 is a perspective view of the completed rung of this inventionprior to its assembly with the ladder siderails;

FIG. 5 is an enlarged fragmentary elevation in partial sectionillustrating the connection of the rung to the ladder siderail;

FIG. 6 is a partial perspective view illustrating a modiiied form of theladder rung of this invention; and

FIG. 7 is a cross-sectional view illustrating still another frnodifiedform of the invention.

Referring now to the drawings and particularly to FIGS. 1 and 2 thereof,a section of a ladder formed in accordance with the present invention isshown having a pair of siderails generally designated by the numeral 10,

and in the form illustrated are of I-shaped cross-section having acentral web portion 12 between a pair of flanges 14. While a light metalsidera-il of this configuration is suitable for use with this invention,it is contemplated that other shapes may be used, such as for example,the siderails may be of C-shaped cross-section or in some instances ifdesired, may be of wood, in which case they would be of a rectangularcross-section. At intervals along the siderails corresponding to spacingbetween rungs, are

provided sets of at least two holes 16 and 17 suitably shaped forattachment of rungs to the web 12 in a manner which will be more fullydescribed hereinafter.

A plurality of rungs 18 are spaced at intervals between thesidera-ils,the cross section ofeach rung defining a plurality of relatively heavyrod-like reinforcing rib portions, there being two such ribs 20 and 21in the embodiment of FIGS. 1 and 2 diametrically opposed andinterconnected by relatively light semicircular wall portions 22 formedintegrally therewith to form a rung of circular externalcross-section.Desirably, the external surfaces of therungs are fluted or serrated toprovide a traction sur- :face on the exterior of the rung.

The walls 22 on each end of the rungs are cut back 7 to leave a portionof the ribs extending as rivet studs 24 and 25 respectively. The studsextend through the apertures 16 and 17 and are expanded over the web 12adjacent the apertures by riveting, to form heads 26 and 27.

As shown in FIG. 1, the angular position of therungs with respect to thelongitudinal center-line 28 of the siderails is such that a line 30passing through the center of the heads 26 and 27 and correspondinglythe axes of ribs 20 and 21 make with the line 28 an angle a. vpreferablyapproximates 15, so that when the ladder is placed against a building orother support in use, the line 30 assumes a ppmximatelyverticalposition. Accord- The angle a ingly, the rib portions 29 and 21 arepositioned, in use, at the extreme lower and upper portions of the rung,the positions of maximum loading in tension and compression respectivelyimposed by central loading of the rung from above. Thus, it will be seenthat in the new and improved ladder rung of this invention, there existsa concentration or relatively heavy cross-section of material at thepoints of maximum stress, permitting an extremely thin wall portioninterconnecting these rib portions and a corresponding reduction inweight as compared to a uniform or conventional cross-section. Further,the extension of the rib portions as studs. extending through theapertures 16 and 17, and the expansion or riveting of the end thereof toform the rivet heads 26 and 27 results in pressure between the heads andtheir adjacent holding surfaces in the siderail web to add substantialstrength to the joint to resist forces in shear, tension, torsion, orbending. Yet, because of the relatively small apertures required in thesiderail web 1 2, the siderail is weakened an insubstantial amount ascompared with prior art teachings. p

The unique method for forming the ladder of the present invention may beunderstood by reference to FIGS. 3, 4 and 50f the drawings. As shown inFIGURE 3, the rungs are formed by extruding continuously a cross-sectiondefining the ribs 20 and 21 and integral wall portions 22 and severingthe extrusion into lengths to form blanks 32. A portion of the walls 22near each end of the blank 32 are cutback such as by machining, abradingor other well known techniques to leave end portions of the ribs 20 and21 extending as studs 24 and 25 respectively. After the rungs 18 arethus formed, they are aligned with the apertures 16 and 17 in thesiderail web 12, inserted therethrougliand the outer ends thereofexpanded or riveted to form the heads 26 and 27. In this manner, thehighly desirable ladder structure is formed and assembled in anextremely simple and economical manner.

In the embodiment of FIG. 6, the rung takes the form of a'channel-shapedwide tread step 34, the cross-section of which is defined by a pluralityof longitudinally extending rib portions 36, formed integrally withconnecting side wall portions 38 and a top wall or tread portion 40having upwardly facing treads 42. As in the first mentioned embodiment,the walls 38 and 40 are cut back at the end of the rung to leaveextensions of the ribs 36 in theform. of-studs 44 to be inserted incorrespondingly spaced apertures in the ladder siderail and rivetedthereto.

A still further preferred modified embodiment of the ladder rung of thisinvention is illustrated in FIG. 7 of the drawings. As shown in thisfigure, a rung incorporating the present invention may be formed havinga quadrangular or trapezoidal cross-section to define anupper wall ortread 46 under which a rib portion 48 is integrally formed, sidewalls 50and a bottom wall 52. A pair of rib portions 54 are provided at thecorners of the walls 50 and 52 to resist the tensile stress imposed onthe lower portion of the rungs when loaded. Again, as in the precedingembodiments, the walls 46, 50 and 52 in use will be cut back to leaveextending the ribs 48 and 54, as rivet studs for connection of the rungto the ladder siderails.

Thus, is will be apparent to one skilled in the art that the foregoingobjectives are completely and effectively fulfilled by the presentinvention. Because of the unique cross-sectional configuration of therungs, an extremely strong and light rung section is afiorded, while atthe tachment of the rung to the ladder siderails. The ability to attachthe rungs by riveting materially enhances the strength. of theconnection because of the inherent qualities which derive from arivet-type connection. In other words, after the studs 24 and 25 areinserted through the apertures 16 and 17 and the ends thereof riveted,not only is the rung held against removal from the siderails by therivet heads 26 and 27, but also thatportion of the stud'which remains inthe aperture is expanded so as to develop extreme pressure against thesides of the holes and thus firmly anchor the rung in place.Accordingly, the resulting ladder is light in weight, exceptionallystrong to Withstand the loads imposed thereon, and further is resistantto the damaging effect of forces resolved into the rung-side rail jointsby rough handling.

Since the present invention may take many diverse forms, it is to bedistinctly understood that the foregoing description is illustrativeonly and not limiting, the true spirit and scope of the invention beingdefined by the appended claims:

I claim:

1. A ladder comprising in combination:

a pair of side rails having sets of holes formed therein atlongitudinally spaced intervals, each of said sets having at least twoholes;

and a plurality of rungs extending between said side rails, said rungseach including an extruded length of light metal of a generally circularcross section defining two rod-like rib portions, said rib portionsbeing diametrically opposed and interconnected by semicircular wallportions, the wall portions at each end of said length being cut back toleave said rib portions extending as studs;

said studs being received in said holes and expanded to connect saidrungs to said side rails, said rib portions and said studs in each ofsaid rungs being spaced along the length of said side rails to provideresistance to bending of said rungs together with resistance to bendingbetween said rungs and said side rails in a direction of length of saidside rails.

2. A ladder comprising in combination:

a pair of side rails having sets of holes formed therein atlongitudinally spaced intervals, each of said sets having at least twoholes;

and a plurality of rungs extending between said side rails, said rungseach including an extruded length of light metal of a channel-shapedcross section, said channel-shaped cross section defining a wide treadstep including four rib portions connected by a pair or integral sidewall portions and a top wall portion, the wall portions at each end ofsaid length being cut back to leave said rib portions extending asstuds;

said studs being received in said holes and expanded to connect saidrungs to said side rails, said rib portions and said studs in each ofsaid rungs being spaced along the length of said side rails to provideresistance to bending of said rungs together with resistance to bendingbetween said rungs and said side rails in a direction of the length or"said side rails.

3. A ladder comprising in combination:

a pair of side rails having sets of holes formed therein atlongitudinally spaced intervals, each of said sets having at least twoholes;

and a plurality of rungs extending between said side rails, said rungseach including an extruded length or" light metal of a quadrangularcross section to define top, bottom and side wall portions, said runghaving rod-like rib portions, at least one of said rib portions in saidtop wall and at least two of said rib portions being disposed at thecorners defined by said bottom and side walls, the wall portions at eachend of said length being cut back to leave said rib portions extendingas studs;

said studs being received in said holes and expanded to connect saidrungs to said side rails, said rib portions and said studs in each ofsaid rungs being spaced along the length of said side rails to provideresistance to bending of said rungs together with resistance to bendingbetween said rungs and said side rails in a direction of length of saidside rails.

References Cited by the Examiner UNITED STATES PATENTS 347,608 8/86Jackson 182-194 488,428 12/92 Frye et a1. 182216 901,755 10/08 Tiepolt182194 1,246,709 11/17 Brown 182-228 2,090,331 8/37 Kutscheid 1822222,630,175 3/53 Dickerman 29-513 X 2,790,586 4/57 Troche 182-2163,016,976 1/62 Munson 182-194 FOREIGN PATENTS 211,308 2/24 GreatBritain.

468,907 7/37 Great Britain.

561,625 10/57 Belgium.

HARRISON R. MOSELEY, Primary Examiner. G. L. BREHM, Examiner.

1. A LADDER COMPRISING IN COMBINATION: A PAIR OF SIDE RAILS HAVING SETSOF HOLES FORMED THEREIN AT LONGITUDINALLY SPACED INTERVALS, EACH OF SAIDSETS HAVING AT LEAST TWO HOLES; AND A PLURALITY OF RUNGS EXTENDINGBETWEEN SAID SIDE RAILS, SAID RUNGS EXTENDING BETWEEN SAID SIDE OF LIGHTMETAL OF A GENERALLY CIRCULAR CROSS SECTION DEFINING TWO ROD-LIKE RIBPORTIONS, SAID RIB PORTIONS BEING DIAMETRICALLY OPPOSED ANDINTERCONNECTED BY SEMICIRCULAR WALL PORTIONS, THE WALL PORTIONS AT EACHEND OF SAID LENGTH BEING CUT BACK TO LEAVE SAID RIB PORTION EXTENDING ASSTUDS; SAID STUDS BEING RECEIVED IN SAID HOLES AND EXPANDED TO CONNECTEDSAID RUNGS TO SAID SIDE RAILS, SAID RIB PORTIONS AND SAID STUDS IN EACHOF SAID RUNGS BEING SPACED ALONG THE LENGTH OF SAID SIDE RAILS TOPROVIDE RESISTANCE TO BENDING OF SAID RUNGS TOGETHER WITH RESISTANCE TOBENDING BETWEEN SAID RUNGS AND SAID SIDE RAILS IN A DIRECTION OF LENGTHOF SAID SIDE RAILS.